The present invention relates to a method and apparatus for controlling an agricultural baling machine when combined with and connected to a tractor and, more particularly, to a method and apparatus for maximizing the work output of a baler by maximizing the flow rate of material through the baler.
In the field of agricultural vehicles it is well known to provide a baler, that is towable behind a tractor, to gather and form into bales biological matter left after a harvesting or mowing operation. xe2x80x9cBiological matterxe2x80x9d as used herein includes but is not limited to straw, grass, hay, forage and silage. xe2x80x9cTractorxe2x80x9d as used herein includes any vehicle capable of propelling and providing power to a baler.
A baler is in use hitched to the tractor hitch and draws power from the tractor power take off (PTO) shaft, for the purposes of gathering and compacting biological matter. The biological matter typically lies in swaths or windows in a field. The baler gathers the biological matter, typically lying over a distance of several tens of meters, into an intake at the front of the baler. The baler compacts the biological matter into a bale of predetermined shape. The baler includes mechanisms for tying the bales with strong twine and knotting the twine; and then ejecting each completed bale, as it is formed, from the rear of the baler.
A development occurred in the baler art in the late 1970""s. This was the introduction of so-called xe2x80x9clarge rectangular balersxe2x80x9d, or xe2x80x9clarge square balersxe2x80x9d. Some known large rectangular balers are capable of producing cubical bales each weighing a ton or more. This represented a significant increase, in baling capacity, over the previously available balers.
However it is becoming increasingly common for operators to use so-called xe2x80x9cMidixe2x80x9d balers that typically produce bale masses in the range 250-750 kg. The invention is particularly but not exclusively suitable for use in such Midi-balers.
During use the pre-compression chamber forming part of a rectangular baler periodically transfers biological matter to a main baling chamber. A piston, in the baling chamber, that reciprocates under power from the tractor PTO shaft, compresses the biological material into a bale whose density is dictated by numerous factors including the volume of each charge from the pre-compression chamber.
Rectangular balers operate most efficiently when the swaths of biological material through which they are towed are of constant density. This ensures that the pre-compression chamber fills at a substantially constant rate. In practical use of large rectangular balers, however, the swath density is rarely constant over an entire field, or even from place to place in a swath. This can be for a number of reasons, including variations in crop density before harvesting; and variations in efficiency of the harvesting process leaving different amounts of biological material in different parts of the swaths. Such variations in the swaths often arise when, during harvesting, a harvesting machine (typically a combine harvester) has to slow down or stop part way along a row of crop. The variations also arise at junctions between swaths, in non-rectangular fields.
Heretofore, the operator of a tractor/baler combination has had to rely on visual inspection of the swaths as the tractor approached them, in order to judge the swath density. If the operator perceived a region of low swath density he would attempt to increase the tractor forward speed to try and temporarily increase the rate of intake of biological material into the pre-compression chamber, with the aim of maintaining a generally constant throughput of biological material through the baler.
Similarly if the operator noticed a region of high density in the swath he would attempt to reduce the tractor speed by an appropriate amount.
This method of regulating the throughput of biological material is inefficient for numerous reasons, including, at least:
a lack of consistency in the remedial action taken to overcome low and high swath densities;
the possibility of overloading the tractor engine when attempting to accelerate the tractor, e.g. as a result of performing transmission shifts that are not timed correctly and hence coincide with peak PTO shaft loadings. This can have an adverse effect on the engine loading and can in any event cause the tractor to slow or stop, thereby affecting work rate;
failure to notice or respond adequately to high swath densities leading to blockages, in the pre-compression chamber, that require halting of the baling operation to clear; and
the tractor operator taking remedial action for too long or too short a period.
In sloping fields the above-noted problems are frequently more acute than in flat fields.
In general it is desirable to maximize work rate during baling operations. One reason for this is that the moisture content of the biological material frequently affects its specific mass, quality and value. It is likely that delays and inefficiencies in baling operations will allow unacceptable moisture content changes, especially in countries, such as those in Northern Europe, whose climates are variable at most times of year.
The prior art discloses several attempts at improving the consistency of the charge supplied from the pre-compression chamber to the baling chamber.
In GB-A-1.575.243 and U.S. Pat. No. 4,034,543 mechanisms temporarily halt both the baling plunger and the stuffer fork that supplies charges of biological material from the pre-compression chamber, when a mass sensor detects underloading of the said chamber.
However, U.S. Pat. No. 4,135,444 notes that the technique of GB-A-1.575.243 and U.S. Pat. No. 4,034,543 is sub-optimal because the need to accelerate and decelerate the massive plunger leads to failure of mechanical components, such as clutches, in the baler.
U.S. Pat. No. 4,135,444 proposes temporary halting of only the stuffer forks, while the plunger continues to reciprocate, until the charge in the pre-compression chamber is adequate. However there is no disclosure in U.S. Pat. No. 4,135,444 of how to accommodate swaths of high density, that lead to overloading of the pre-compression chamber and/or the tractor engine.
Also, none of the aforementioned documents discloses an apparatus or method whose aim is to maximize the overall work rate of the tractor/baler combination; nor does any of them disclose a method or apparatus that may compensate for the effects of field slope on baler throughput.
It is an object of the present invention to overcome the aforementioned disadvantages of the prior art by providing a method and apparatus for controlling the operation of a baler by monitoring the flow rate of the baler and adjusting the speed of the tractor towing the baler to optimize the crop throughput.
It is an feature of this invention to comparing the assessed flow rate against an optimal flow rate, and adjusting the tractor speed in dependence on the outcome of the comparison.
It is an advantage of this invention that the tractor speed is changed only when necessary, as determined by the assessed flow rate of biological material.
It is another object of this invention to adjust the flow rate of the baler by adjusting the tractor forward speed, both when the flow rate of material through the baler is too high and when the flow rate is too low.
It is another feature of this invention that the method of controlling the tractor/baler combination optimizes flow rate and prevents blocking of the pre-compression chamber.
It is still another object of this invention to repeat the method steps cyclically in dependence on the pulses of the clock of a microprocessor arranged to carry out the method.
It is still another feature of this invention that the correction effected by adjustment of the vehicle speed may take effect only for the duration of the sub-optimal flow rate through the baler.
It is yet another object of this invention to use transmission shifts to change the speed of the tractor thereby allowing the tractor engine to run at constant speed.
It is still another advantage of this invention that the PTO shaft speed of the tractor does not vary significantly while the speed change takes place.
It is yet another advantage of this invention that the use of transmission shifts permits a method that minimizes the risk of overloading or over-revving the tractor engine.
It is yet another feature of this invention to allow minor variations in the flow rate of biological material through the baler without the need for the tractor transmission ratio to shift incessantly.
It is another object of this invention to modify the speed of travel of the tractor by monitoring defined variables in the biological material passing into and through the baler.
It is still another feature of this invention that the tractor engine load is compared to a limit value before incrementing the transmission.
It is a further advantage of this invention that the method of controlling the tractor prevents engine overloads on ratio change-up.
It is yet another feature of this invention that the slope of the ground is taken into consideration in changing the operational speed of the tractor.
It is a further object of this invention to use a reference model through the use of a microprocessor to carry out the prediction.
It is a further feature of this invention that the reference model has stored therein one or more lookup tables in a memory forming part of or operatively connected to the microprocessor.
It is still a further feature of this invention that a flywheel torque sensor is used to define the load on the tractor engine.
It is yet a further feature of this invention to predict the load on the tractor engine a plurality of times thus eliminating misleading instantaneous loadings that may otherwise cause unnecessary transmission shifts.
It is still another feature of this invention to decrement the transmission ratio more rapidly that incremental changes to avoid extreme forms of tractor engine overload that can cause plugging of the pre-compression chamber and/or shearing of a shear bolt, commonly present in balers, to protect the drive train for the stuffer forks.
It is yet a further object of this invention to increment and decrement the transmission ratios when the reciprocably moveable baler plunger occupies a predetermined position.
It is yet a further feature of this invention that the predetermined plunger position is chosen to avoid superimposing the torque loading arising from the gear change onto the peak loading from the plunger cycle.
It is still another feature of this invention to allow the signals processed by the microprocessor to be substantially or entirely independent of the bale density.
It is another advantage of this invention to sample the sensor door position when the baler plunger is between approximately 100xc2x0 and 150xc2x0 from its front dead center position.
It is still another advantage of this invention to measure the flow rate of the baler by detecting the PTO shaft torque.
It is a further advantage of this invention to sample the PTO shaft torque the baler plunger is between about 350xc2x0 and 50xc2x0 from its front dead center position.
These and other objects, features and advantages are accomplished according to the instant invention by providing a method of controlling the combination of a baler and a tractor including the steps of advancing the baler combination through a swath or windrow of biological crop matter with the tractor PTO operating at a generally constant speed to power the baler and the baler operating to take up biological matter while monitoring the flow rate of the biological matter through the baler. A microprocessor compares the assessed flow rate with an optimal flow rate and varies the travel speed of the tractor to maximize the flow rate of crop material through the baler. Preferably, the speed of operation of the tractor is accomplished through changing transmission speeds so that the PTO shaft speed is maintained at a substantially uniform rotational speed. The apparatus provided for carrying out the method of controlling the combination of a tractor and a baler increases the work rate of baling operations.